mutation in which extra base pairs are inserted into a new place in the DNA.Types of mutations
Insertion .
Deletion .mutations in which a section of DNA is lost or deleted
.

 frameshifts • Frameshift mutations generate incorrect or truncated proteins
.Effect of insertion and deletion mutations: frameshifts
• Insertions and deletions can alter a gene so that its message is no longer correctly divided.

Chemical mutagens
• Base analogs
– can be incorporated into DNA and form transient tautomers – Can lead to transition mutations
• Base modifiers
– Chemically modify DNA bases
• DNA intercalators
– slip in between adjacent base pairs in dsDNA – lead to the insertion or deletion of one or more base pairs – Results in frameshift mutations
.

Mechanism of mutation induced by 5-bromouracil. a base analog
.

is activated by cytochrome p450 to form a highly reactive mutagenic compound
. produced by molds that grow on peanuts.Mutagen metabolism
• Aflatoxin.

. inducing a transition from A-T to G-C.Base modification
• Treatment of DNA with nitrous acid results in the conversion of adenine into hypoxanthine. • Hypoxanthine pairs with cytosine.

Base – modifying agents
.

. leading to the incorporation of an additional base on the opposite strand.Intercalating agents
Acridine dyes induce frameshift mutations by intercalating into the DNA.

Antioxidant defense system
• Includes vitamins E and C. and the carotenoids (pigments present in colored vegetables and some colored fruits) • Higher intakes of these nutrients are associated with lower rates of cancer and cardiovascular disease
.

occur in reproductive cells like eggs and sperm
The only mutations that matter to evolution are those that can be passed on to offspring.
.g.. i. Germline mutations . Its seeds will not carry the mutation.e.. germline mutations.Mutation effects depend on affected cell type
1.
2.
e. the golden color on half of this Red Delicious apple was caused by a somatic mutation. Somatic mutations .occur in non-reproductive cells and won't be passed on to offspring.

can result in proteins being made at the wrong time or in the wrong cell type 2. can also result in too much or too little of the protein being made.Types of mutations
DNA expression mutation
• Protein itself is not changed • Effect is on where and how much of a protein is made 1.
.

• Mutations in control genes can substantially change the way the organism is built.
.Mutations in control genes
• Mutation in a gene "conductor" can cause a cascade of effects in the behavior of genes under its control.

a control gene.Effects of mutations in control genes
• Hox. • Scientists have studied flies carrying Hox mutations that sprout legs on their foreheads instead of antennae!
. designates where the head goes and which regions of the body grow appendages.

. • If a single mutation is required to trigger cancer and this mutation had an equal chance of occurring at any time.A single mutation is not enough to cause cancer
• Cancer incidence rises steeply as a function of age. the incidence would be independent of age.

A tumor develops through repeated rounds of mutation and proliferation
.

chemical carcinogens 2. viruses
. ionizing radiations such as x-rays 3.Cancers result from somatic mutation
• damage to DNA a fundamental event in carcinogenesis • Clear correlation for three classes of agents:
1.

not directed
• Mutations can be beneficial. mutations are random — whether a particular mutation happens or not is unrelated to how useful that mutation would be.
e.g. exposure to harmful chemicals may increase the mutation rate.
. BUT do not "try" to supply what the organism "needs.Mutations are random. neutral.
THEREFORE. or harmful for the organism.." • Factors in the environment may influence the rate of mutation but do not influence the direction of mutation. but will NOT cause more mutations that make the organism resistant to those chemicals.

including pain and anemia
• The disease is caused by a mutated version of the gene that helps make hemoglobin — a protein that carries oxygen in red blood cells (RBCs).Sickle cell anemia: a case study of the effects of mutation
• Sickle cell anemia: a genetic disease with severe symptoms.
• Gene is homozygous recessive
.

allowing it to clump together.Sickle cell anemia: a case study
• There are effects at the DNA level
• There are effects at the protein level
The mutation in the DNA slightly changes the shape of the hemoglobin molecule.
.

a carrier of the sickle cell allele may occasionally show symptoms such as pain and fatigue. This shape can sometimes interrupt blood flow. There are positive effects at the whole organism level Carriers of the sickle cell allele are resistant to malaria.
•
Normal red blood cells
•
sickle cells
. There are negative effects at the whole organism level Under conditions such as high elevation and intense exercise. they become "sickle-shaped" . because the parasites that cause this disease are killed inside sickle-shaped blood cells.Sickle cell anemia: a case study
• There are effects at the cellular level When RBCs carrying mutant hemoglobin are deprived of oxygen.